This is a direct listing. Sure they could open up a private market so their investors could sell for Bitcoin, but:
1. I bet most shareholders already have plenty of crypto and should diversify.
2. Opening up a private market for Bitcoin-only sales really doesn’t help liquidity much.
It’s important to remember - this wasn’t a move for Coinbase to raise money, it was to enable people who have shares in Coinbase to be able to more easily sell.
Really says a lot of their faith in Crypto's future.